Q: 10
You work for a car manufacturer and have set up a data pipeline using Google Cloud Pub/Sub to
capture anomalous sensor events. You are using a push subscription in Cloud Pub/Sub that calls a
custom HTTPS endpoint that you have created to take action of these anomalous events as they
occur. Your custom HTTPS endpoint keeps getting an inordinate amount of duplicate messages. What
is the most likely cause of these duplicate messages?
Options
Discussion
Option B actually makes sense here. If the SSL cert is out-of-date, Pub/Sub’s push will get handshake failures and treat it like a non-ack, which leads to retries and so you get duplicates. I know D's also common but in this scenario, cert problems will cause exactly this issue. Pretty sure B is right-correct me if I’m missing something.
Nah, I don’t think it’s D here. B is the catch-Pub/Sub push fails when certs are invalid, so messages aren’t acknowledged and you get retries (hence duplicates). D is a standard culprit but this question points at HTTPS/SSL issues.
Its D, not B. Pub/Sub will keep retrying if your endpoint isn't sending an ack fast enough, classic trap here.
Guessing D. Pub/Sub resends unacked messages so if your endpoint isn't acknowledging them in time, you'll get duplicates.
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